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    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
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  <body>
    <script src="./lodash.min.js"></script>
    <script>
      function f1() {
        const f2 = function () {
          let x = 10;let y = 10;
          let age = x + y;
          return age;
        };
        return f2;
      }
      const fn = f1(); // f1执行完毕
      console.log(fn()); //f2(); age 常驻内存
    </script>
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